1. Field of the Invention
The present invention relates generally to controlling blood pressure. More particularly, the present invention relates to devices and methods for controlling blood pressure using a retrograde cannula.
2. Background of the Invention
The concept of myocardial salvage through coronary sinus intervention dates back to the nineteenth century. The objective has been to increase the flow of oxygenated blood to the ischemic myocardium by perfusing the coronary bed retrogradely from the coronary sinus; i.e., coronary retroperfusion. To date, a number of retroperfusion methods have been developed. Pressure-controlled intermittent coronary sinus occlusion (PICSO) has been used in conjunction with a balloon-tipped catheter positioned just beyond the orifice of the coronary sinus with the proximal end connected to a pneumatic pump that automatically inflates and deflates the balloon according to a preset cycle. Synchronized retrograde perfusion (SRP) and simplified retroperfusion are other techniques that actively pump arterial and venous blood in the former and the latter, respectively. The left ventricle-powered coronary sinus retroperfusion technique has focused on driving left ventricular blood into the coronary sinus through a surgically created left ventricle to coronary sinus shunt.
Prior studies have shown the efficacy of venous retroperfusion. It has been demonstrated that (1) coronary venous bypass-graft (CVBG) or percutaneous in situ coronary venous arterialization (PICVA) permits survival in the presence of LAD arterial ligation as compared with the uniform non-viability of just LAD arterial ligation without retroperfusion; (2) retroperfusion is effective because it perfuses all layers of the heart, including the subendocardium; and (3) considerable recovery of regional myocardial function with low regional capillary blood flows and low levels of retrograde arterial outflow provide evidence for possible oxygen delivery via the intramyocardial venous plexus.
The CVBG or PICVA procedure has a number of advantages over the conventional coronary artery bypass graft (CABG) procedure, because, at least in part: (1) approximately 20% of revascularization candidates have angiographically diffuse atherosclerotic changes with poor runoff or small coronary arteries which makes arterial bypass or percutaneous coronary angioplasty unlikely to succeed. In those cases, CVBG may be the procedure of choice. Furthermore, the runoff for the coronary veins are significantly larger than those of arteries and hence the surgical implementation is much easier as is the improved patency of the graft. (2) The coronary venous system of the heart rarely undergoes atherosclerotic changes. This reduces the problem of restenosis that is commonly evident with the CABG procedure and should reduce the need for multiple surgeries throughout the patient's lifespan. (3) The CVBG is surgically easier to implement than the CABG procedure and does not require cardiac arrest and the use of extracorporeal circulation. The CVBG procedure can be implemented in the beating heart with the use of a cardiac restrainer. This reduces the surgical risks and ensures quicker recovery, which is particularly important in the elderly and the severely ill patients.
To emphasize the importance of this field in terms of numbers, at the time this application was filed there were about 1.4 million annual incidences of myocardial infarction in the U.S. and an equal number in Western Europe. Approximately 20% of those patients were not good candidates for bypass because of diffuse coronary artery disease and, accordingly, had few treatment options other than heart transplant. The number of heart transplants is meager, however, about 2,000 in 2005. Many of those patients progress to heart failure and thus incur the very high cost of treatment associated therewith ($40 billion annually in the United States, representing 5.4% of total health care cost). The prospect of a device to treat such patients is great in terms of lives saved as well as costs reduction associated with heart failure.
Thus, a need exists in the art for an alternative to the conventional techniques of treating heart failure using retroperfusion such that the technique should be minimally invasive, easy to use and understand, simple to implement and effective in producing desired results.